Loss of memory is one of the most dreaded afflictions of the human condition. Devastation hurled upon the human brain by trauma, stroke, epilepsy or processes of degenerations afflict a vast number of people in the US and worldwide. Traumatic brain injury (“TBI”) is a leading cause of disability in young adults. Over 5.3 million people in the US live with long-term disability as a result of TBI and 70-80% of them are impaired by memory deficits. Memory impairment is strongly linked to the ability of TBI survivors to return to work and live independently. Moderate to severe memory impairment is also a feature of epilepsy, which affects over 2 million people in the US, many of them under 45 years of age. With progress in neuroscience and engineering, further discoveries in the neural substrates of human memory, and the emergence of novel neurotechnologies, the developments of therapies aimed at restoration of memory have become a major medical and social priority.
With advances in technologies to probe the human brain, electrical stimulation has emerged as a potential avenue for therapeutic intervention. However, the effects of brain stimulation on behavior are highly dependent on the precise location of delivery. For example, deep brain stimulation (“DBS”) for treatment of Parkinson's disease is most effective when delivered to highly specific regions within the basal ganglia, such as the subthalamic nucleus and the globus pallidus, while DBS for depression is useful when delivered to the subcallosal cingulate gyrus.
Activation of previous experiences or memories has been shown to result from DBS of memory related brain circuits such as those within the temporal lobe. Electrical stimulation of areas in the temporal lobe can cause a small percentage of patients to report feelings of familiarity (also sometimes called “déjà vu”) and the re-experiencing of old memories. Electrical stimulation of similar sites in the ventral temporal lobe has also resulted in the reporting of past experiences and sometimes the vague experiences of déjà vu. Extra-temporal stimulation of the hypothalamus has also been shown to create experiences of déjà vu and enhance verbal memory in a single patient. However, there is a lack of control over which memories are to be re-experienced or whether these are in fact specific memories from the past.